The thawed ice area jumped from 40% of the ice sheet to 97% in just four days from 8 July.

Although about half of Greenland's ice sheet normally sees surface melting over the summer months, the speed and scale of this year's thaw surprised scientists, who described the phenomenon as 'extraordinary'.

NASA said that nearly the entire ice cover of Greenland, from its thin, low-lying coastal edges to its centre, which is 3km (two miles) thick, experienced some degree of melting at its surface."